Sound Effects Recording & Sound Design Blog

Electromagnetism

Introduction:

Electricity · Magnetism

Electromagnetic fields are present everywhere in our environment but are invisible and silent respectively to the human eye and ear. As you probably know, Electric fields are created by differences in voltage: the higher the voltage, the stronger will be the resultant field. Magnetic fields are created when electric current flows: the greater the current, the stronger the magnetic field..

So any electrical source generate a time-varying magnetic field that is proportionally identical in frequencies and amplitudes to the source. This is the theory behind all the speakers, dynamic microphones and also guitar pickups.

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$80 Seymour Duncan custom pickup

$10 No brand custom pickup.

The Seymour Duncan pickup has a better Signal-Noise ratio and almost doesn’t make any hum because of his twin coil design. Soldering the white one is very easy but you’ll need wiring instructions if you plan to get a Seymour Duncan.

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Electric Sources:

Pickup schema

Those are a few examples only. Because pick-ups don’t need any power, I soldered an XLR to 1/8 inch cable so that I can hook them up to my Sony D-50 and carry it in my pocket. I usually throw them anywhere I see an interesting source of energy (engine compartment of a car, photocopier, transformers, electric poles, network routers and links etc…). You can listen to the signal made by your remote when you press a key, your camera adjusting the lenses or the flash loading, a spinning hard-drive or the sound of your RAM writing data in your computer, a satellite antenna etc…

One of the biggest advantage of this technique is that it is not sensitive to wind, handling noise and background environment. But it’s sometimes harder than you think to isolate a big hum generated by the AC when you’re focused on the servo of a printer. I’ve destroyed my cellphone and froze the RAM of my laptop though, so please read the caution below before starting any experiments.

CAUTION:

Powerful magnets can affect the operation of pacemakers and other similar medical devices. A guitar pick-up must never be placed near a person with such a device. Powerful magnets can also damage electronic devices such as TVs and CRTs. They may also scramble data on magnetic media such as hard disks, credit cards, ID cards and cassette tapes.

i’m going to look for some pickups i took off my Les Paul. i just like to know what to wire configuration that you used to attach it to an XLR? looking at the diagrams on the Duncan web site, green/bare looks like the ground, and for a dual rail pickup (humbucker), all that is attached is the black, with the red white soldered together. is the XLR pin 1: green/bare, and pin 2: black with nothing attached to pin 3? you can email me direct if you like. i also don’t know what the output of the pickup will be. closer to line or mic levels?
cheers et merci,
P.

@ George: As you can’t see and can’t hear magnetic fields, the best way to record it is to try to put the pick up anywhere you can. Depending if it’s a time varying sound or a constant drone, you’ll choose either to record 30 sec of your best spot and change or move the pick up around you source like a light saber. Unfortunately, you won’t have any doppler effect, just an amplitude change. It’s really fun to record because you never know what you’ll get.

@ pepe: Every pick-ups are different and they often have different wiring configurations depending on your needs. Looking at the Duncan website is definitely the best thing to do first. I’ve tried different configurations with mine and finally ended up with 1: bare, 2: green, 3 black and solder/shrink all the rest. I’ve never managed to get a line or mic level out of it (I assume because there’s no preamp) but let us know if you get any better results!

Good Stuff! I’ve done a bunch of recording like this. Lots of fun to spin up an old (aka I don’t need it anymore) hard drive and get some awesome sounds. Small fans (with magnetic motors) can be fun too!.

Great post. If you want to record EM fields without using magnets, you can use a small coil of wire instead. Radio Shack sells one with a little suction-cup on it, called a “Recorder Telephone Pickup”. Also, I’ve been experimenting with VLF radio reception (which includes the energy you’re talking about) and I’ve found some wonderfully simple FET preamp designs on the web that will plug right into an 1/8″ input with plug-in power. I did some experiments here:http://www.zachpoff.com/site2/diy-resources/vlf-natural-radio-experiments

Don’t touch the metal parts of your pick up with any metal elements of a high voltage conductor and don’t go too close to any high voltage source with such a device. You could get electrocuted as the pick up is a perfect antenna for any lightnings and bolts. I’m sure you know it but I’m just covering my ass here. In any over case, your recorder should be fine.

hey,thx for the reply. well, I just asked, because I saw the video at sonic terrain where you get close to something that looked like high voltage cables. But I guess I just have to be very careful and always watch out not to get too close to things like that=)

@Zach Poff, the “Recorder Telephone Pickup’s from Radio shack are amazing. I recently recorded the XBOX, Playstation, and Nintendo Wii boxes with them. Some of the power ups, from the Nintendo Wii are incredible. I carry them in my sound devices bag with me everywhere:)

the link on top is to one of my projects.
i was picking up the em-fields with a special detector – the “e-smog detector”.
next time i try to work with telephone pick-up coils. they are nearly the same as
the guitar pick ups that u use.

this is really inspiring.
thank you for a good blog.
can you please tell me exactly what kind of seymour duncan pickup you are using??
i tried to look for it on their site, but its a whole sea of choices out there.
and to be honest, i dont really want to buy a lot of pickups, just to find the wrong ones. off course, i know, that any pickups have their own Characteristics, but please help me out here.
yeah.
-h

Hi Loïck,
I’m not an expert with guitar pick-ups. But yes, I believe a stereo pick-up means it is balanced. I did some stereo recording experiments with two pick ups. if you watch that video (http://jedsound.com/blog/?p=368) you’ll see a long snaky spring recorded in the stairwells with a pick-up set up at each end. I usually do the same for any king of springs, slinky etc because you get a clean impact and the descending tone that follows. Let us know if you get interesting results.

@Nicolas,
I only used Gain. No EQ or noise removing treatment. You’re probably not close enough to the source of what you’re trying to record. I’d suggest you to move the pickup all around your device and define where the best spot is. Then if you’re not close enough, you might have to open the body of your device. Cheers!

Hi there!
I’ve discovered your work on a sound design site and I can say that I’m a big fun of your work, really inspiring.
Recently I’ve discovered that an old doublebass pickup that I own is really sensible in magnetism so I try out different sources and I discovered that a cdj player produce a loud noise if I put the pickup above it.. I processed that sound and what cames out was this song, the bass line and the drums where made processing that signal through guitar stompboxes: http://www.youtube.com/watch?feature=player_embedded&v=37Xzv8zD6EA
Sorry for my bad English man, take care,

Cool, thank you for sharing your ideas and your song ARNOUX! Good job, keep it up!

If you don’t mind, I’ll correct what you just said “I discovered that a cdj player produce a loud noise if I put the pickup above it”.
The human ear is in fact not able to hear the spectrum of a magnetic source. Your pickup though is designed to perceive perturbations of it in proximity. Those perturbations are captured and converted into low current and amplified by your pre-amp. Then, it’s basically just a variation of electricity that is then even more amplified so that your speakers can create an equivalent perturbation of the atmospheric pressure that can be this time, perceived by your ears.

Hey this is great I can’t wait to experiment with it, but I was wondering if you could explain how you damaged your phone and computer and how to avoid electrocution danger. Thanks for the cool project